Pollution reducing aircraft propulsion

ABSTRACT

Aircraft engine exhaust is mixed with air and fuel and recombusted. Air is drawn into the secondary combustion chamber from suction surfaces on wings. Exhaust of the secondary combustion chamber is blown over wing and fuselage surfaces.

BACKGROUND OF THE INVENTION

This is a continuation of patent application Ser. No. 532,646, filedDec. 13, 1974, and patent application Ser. No. 788,526, filed Apr. 18,1977, by Raymond M. Tamura, entitled Pollution Reducing Aircraft nowabandoned. This is a continuation-in-part of patent application Ser. No.788,528, filed Apr. 18, 1977, by Raymond M. Tamura, and entitledHelicopter Lifting and Propelling Apparatus.

With greater pressures from the Environmental Protection Agency toregulate turbine emissions, there is an urgency in seeking solutions foreconomical propulsive methods. Low nitrogen oxide levels dictated by theEPA are incompatible with present turbine power plants. Turbineefficiency dictates fuel combustion at higher and higher temperatures.That approach to efficiency creates greater quantities of nitrogenoxides, as well as oxides of sulfur, phosphorus and chromium.

The aviation industry is faced with the tasks of using less fuel and ofburning fuel at lower temperatures, which mean incomplete combustion andlowered efficiency. The present invention seeks to accomplish thosetasks.

SUMMARY OF THE INVENTION

The present invention is a system which produces high lift duringtake-off and landings and which reduces friction and parasite dragduring cruise without excessive fuel consumption. The present systemutilizes the partially unburned fuel of a reciprocating engine,turboprop engine, jet engine or turbofan engine to power a turbine whichsuctions and blows air over wings, area-ruled regions of the fuselageand over vertical and horizontal stabilizers.

This system increases efficiency in a two-fold manner. It extracts thegreatest possible quantum of heat energy from a given aliquot of fuelinjected into the primary propulsive engine. By reducing friction drag,a given quantum of propulsive power is translated into greater velocityor greater lift.

One embodiment of the invention is described with relation to turbinepower plants which are representative of present state of art. In aturboprop system the entire exhaust mass is directed to the combustionsection of a compressor-suction turbine. This exhaust from the turbopropis swirled and is mixed with bleed air from the compressor of thecompressor-suction turbine. Fresh fuel also is swirled with thismixture. The combustor will be of sufficient length to permit completecombustion.

The quantity of fresh fuel in the compressor-suction turbine is on theorder of 0.1 or 0.2 specific fuel consumption, while the turboprop maybe of the order of 0.5 to 0.6 specific fuel consumption.

Exhaust from the compressor-suction turbine is ducted to filleted areasof the fuselage-wing junction to smooth air flow and is ducted to thearea-ruled region of the fuselage for reducing wetted area as well asfor increasing air flow velocity.

The compressor section of the compressor-suction turbine is tied into asystem which suctions boundary layers of the wing. This compressor'sprimary air mass is led to wing ducts which blow air over the wing in achord-wise direction. That reduces friction drag, since the shear forcesbetween two fluid layers moving in the same direction are much less thanshear forces between a solid surface and a fluid media. This is mostcrucial during cruise. It is operative during take-off and landing sothat lift is increased.

In an embodiment used in a turbojet system, the primary exhaust mass isejected out of the tail pipe as in any other turbojet. Combustion gasescool rapidly after the passing through the turbine - especially thatlayer adjacent to the tail pipe wall. There, combustion has practicallyceased. NASA type ducts bleed off that outer layer in the exhaust pipeand direct that mass to the combustion section of the compressor-suctionturbine where identical events occur as described earlier.

In a turbofan system embodiment, boundary layer exhaust mass is bled offand directed in the same manner to the compressor-suction turbine. Butin the turbofan, some air mass is bled off the fan section as well asthe compressor section. Again, the same events occur in thecompressor-suction turbine as explained earlier.

The exhaust from a reciprocating engine is also ducted to acompressor-suction turbine where more complete combustion can occur.Manufacturers of these engines face the same prohibitive restrictions asthe turbine manufacturers.

The present system has major differences from past attempts at blownwings. The entire wing surface is blown and suctioned during cruise aswell as during take-off and landing. Ducts which suction and blow airare integral, weight-bearing structures. Because of thecompressor-suction turbine, a slight increase in specific fuelconsumption must be borne in reducing effective wetted areas and therebyin reducing drag. The suctioned and blown boundary layer has less shearvectors opposing one another. A laminar flow airfoil is used in anexample, but a supercritical airfoil also benefits from this system,since turbulence is attenuated and the critical boundary layer isshifted further toward the trailing edge or beyond it. This pushescruise velocity to a higher subsonic value.

The blower and suction ducts are stringers and integral parts of theprimary wing structure. This method avoids the problems created byhaving separate ducts. A three spar structure is proposed for fail-safereasons. Wing skin plates are bonded or brazed to the ducts and ribs.The wing is set and can be urethane foam-filled for militaryapplications.

Leading edge slats are automatic in a preferred embodiment. The suctionducts smooth turbulent flow when the slats are extended. Full-spandouble slotted flaps are blown during take-off, landing and mostsignificantly, during cruise. Blown air energizes the very last segmentof air flow over the top surface and thus creates a differentialpressure which adds to the lift vector during cruise, thereby reducingpower requirements.

Unlike blown flap systems, which are not operational during cruise, thepresent system has the blower duct integral wth the wing primarystructure. As the flap is retracted, it abuts against the duct, which isslotted, sealing the slot. The forward flap segment is channeled to abutagainst the blower duct. This channel is open to the slot in the flapand blows air over the top surface during cruise. When the flap isextended, air continues to be blown over the flap, and in addition, thechannel in the forward segment directs air over the top surface of theflap.

The concept of a blown wing has been used in the past and is being usedat the present. Past and present systems are used only during thelanding and take-off phases of operation. Past and present systems aredesigned only for creating lift.

The system described herein is designed to create lift as well as toreduce drag. This system is operative in all phases of flight;especially during cruise, which is the greatest segment of flight. Animportant feature of the invention is the fact that the ducts which areused for suction and blowing of boundary layer air are primary loadbearing and therefore are structurally integral with the primary wingstructure. This permits a light-weight design. Past and present effortsin this area had non-structural ducts which were not primary loadbearing members and therefore not structurally integral. These wingswere heavy because of that extra plumbing. Past and present systems haveseparate primary propulsive engines and suction/blowing engines. Noenergy from the primary propulsive engine is used in the suction andblowing engines. The present invention utilizes unburned fuel from theprimary propulsive engine. This unburned fuel is used in thesuction/blowing engine. The present invention also utilizes exhaust fromthe suction/blowing engine to reduce drag over fuselage and controlsurfaces. This is accomplished by ducting exhaust to these areas. Someof the blown air is used for this purpose.

Systems which may use ram air from the leading edge ducted to the uppersurface of the wing do not have the present invention if ducts are notprimary load bearing structures. Ram air systems may operate during allphases of flight, but the aircraft has to be in forward motion beforethey function.

The differences in the present invention are due in part to the factthat this system sucks boundary layer air and blows it over the surfacethrough primary load bearing structures. Air is accelerated by asuction/blowing engine. The present system functions even though theaircraft does not have foward motion.

The rationale for suction of boundary layer air is delineated by ModernDevelopments in Fluid Dynamics, Vol. II, edited by S. Goldstein.According to that text, induced drag of fluid flowing over surfaces iscaused by separation of a laminar boundary layer. This separation can beprevented, even in the presence of quite large pressure gradients, by arelatively small withdrawal of air from the boundary layer at or nearthe point where separation occurs. The quantity of air which must beremoved may be as little as 5 percent of the total air mass in theboundary layer passing the suction duct. The suction device toaccomplish this task need have an efficiency of only 75 percent, and thework required to remove this quantity of air is as little as 3.4 percentof the boundary layer kinetic energy at the point where the suction ductis located.

Thus, the suction/blowing device of the present invention need not be aslarge as the primary powerplant. This makes the present system unlikesystems which use a primary propulsion engine to blow the wings. Whilesuch devices consume as much fuel as a primary propulsion engine, thepresent suction/blowing device increases fuel consumption by 0.1 to 0.2specific fuel consumption. This device can be operated continuouslywithout severe fuel penalties. Since this device uses incompletelyburned fuel from the primary propulsion engine, overall efficiency isincreased, and there is drastically reduced environmental pollution withnitrogen oxides, carbon monoxide and other harmful combustionby-products.

Modern Developments in Fluid Dynamics states that best results areobtained with the suction slot 53.9 percent of the chord back from theleading edge, and that slot width should be 0.67 to 3.8 percent of thechord.

The present wing does not follow that placement regimen because thiswing is combined with blowing, and this sytem is designed for decreasingdrag as well as generating lift. The present suction slot is 0.67percent of the chord. This is varied for specific wing sections anddesigns.

The text on fluid dynamics treats lift and drag as separate entities.Suction and blowing are also dealt with separately.

In the invention, lift and drag as well as suction and blowing occursimultaneously.

The International Dictionary of Applied Mathematics states, ". . . It isnecessary to assume that some disturbances are present in the initiallaminar flow, even if these are extremely small. In practice,disturbances may be caused by very slight roughness of the surface,turbulence of the main stream or sound waves." "When the laminar flow isunstable, disturbances are amplified as they proceed downstream andeventually "spots" of turbulent flow appear . . . . "As the spots ofturbulence proceed downstream they grow in size, so that for points inthe boundary layer further downstream the flow is turbulent for agreater proportion of the total time. Eventually, a point is reach,sufficiently far downstream, where the flow is turbulent all the time .. . . "

The present system blows air over the posterior aspects of the wing onupper and lower surfaces. This smooths out the boundary layer bydecreasing these turbulent spots. Mathematically, this process modifiesthe Navier-Stokes equations of motion for a fluid in which viscousstress is proportional to the rate of strain: ##EQU1## The upper linerepresents the inertia force of unit mass. The terms in the lower linesrespectively identify a pressure gradient force, the body force per unitmass, viscous stresses resulting from straining or distorting the fluid,and contribution to the gradient of normal pressure resulting from aspatial variation of the dilation Δ (or rate of cubical expansion;Δ=∂u_(i) /∂x_(i) =divv)

The last term is zero in incompressible fluids and is usually neglectedexcept in compressible flows with large accelerations. Since air iscompressible and flows with large accelerations, this applies toaircraft structures. The term, ν, is the dynamic viscosity. In vectornotation, the equations are written ##EQU2## which may be rearranged inthe form ##EQU3## The present system modifies several terms of thisequation. Suction reduces pressure gradient force over the anteriorsurfaces, since suction removes slow moving air mass which progressivelypiles up as we measure posteriorly from the leading edge. Suction alsoreduces straining of the fluid as noted in the second term.

Blowing air over the posterior aspects of the wing modifies terms bydifferent mechanisms. The pressure gradient force is reduced byentraining air mass flowing past the point of maximum pressure, and thisaccelerates air mass to the rear, removing pressure created by a pilingup of air mass. Another mechanism is the reduction of sheer (friction)stress between wing surface and fluid. Althouh blown air velocity neednot be equal to the velocity of air moving over the surface, sheerstress will be much less than with an unblown wing. Thus, the first,second and third terms are modified by these mechanisms. Blowing airwill also reduce the fourth term by reducing the recirculation of air tothe leading edge and by reducing the spatial variation of the dilationΔ.

In a preferred embodiment of the invention, aircraft wings have blowerand suction ducts which extend through the wing beneath the skininterconnecting ribs. The ducts support the skin in fixed airfoilconfiguration. Preferably the ducts have outward directed elongatedslots which extend through the airfoil skin. The skin of the airfoil inone form of the invention is elongated thin aluminum sheets which aresecured between adjacent ducts, with slots exposed between adjacentsheet edges.

In one preferred form of the invention the blower ducts are constructedin somewhat tear-shaped cross sections with relatively bulbous partsfacing inward and forward, and tapering rearward with smoothly curvedrelatively flattened out surfaces conforming to the airfoil shape. Theouter surface is recessed to receive edges of the skin sheets.

Gas moves longitudinally through a large passageway in the bulbousportions of the ducts. Ducted gases exit laterally though narrowpassageways to the outward slots.

In a preferred form of the invention the blower ducts are arranged atintervals along the wing surface, which intervals generally decreaserearwardly, so that the spaces between slots at a rear surface of theairfoil is less than spaces between the slots at a relatively forwardportion of the airfoil surface.

Suction ducts communicate with and support the upper wing surfacebetween the leading edge and a ling of maximum foil thickness. In apreferred embodiment blower ducts are connected across the remainder ofthe wing. Blower ducts are provided near the trailing edge of a wing anda rearward blower duct has slots which blow gasses across surfaces of atrailing edge flap.

The suction duct has the same shape as the blower duct, in oneembodiment. In a preferred form the blower duct has a rearward taperingtear-shaped cross section, and the suction duct has symmetrical U-shapedcross section.

All of the ducts are structural members, which preferably act asstringers to transfer loads between the airfoil surface and the ribs ofthe airfoil. Consequently, little weight is added to the airfoil by theduct system.

In one embodiment of the invention the duct system and the skin areintegrated in an apparatus with a substantially flat slotted surface andwith the ducts form a raised pattern on the inside surface. In anotherembodiment of the invention the duct slots are integral with the surfaceformation and form a foraminous surface. In another form of theinvention the actual airfoil surface is not smooth but the aerodynamicsurface formed by the blown air cooperating with ambient air issmoothed.

In a preferred form of the invention the ducting and blowing and suctionslots are provided in all aerodynamic surfaces of the aircraft includingthe wings, fuselage and empenage and primary and secondary controlsurfaces and, surfaces interconnecting the parts of the aircraft.

The system of the present invention is useful with all aerodynamicsurfaces and is useful with all wing plan forms and sections includingthose especially designed for subsonic, transonic and supersonicoperation.

In a preferred form of the invention the gas blown through the ducts ischilled to cool the wing surface and thus promote laminar flow of theambient air. The chilling of the gas is accomplished by heat exchangersin which heat is dissipated by cabin heating and interior space heating.The gas in the blowing ducts is cooled before eoing distribution bycontacting the gas with chilled fuselage surfaces and by otherwiserefrigerating the gas.

Blower ducts at primary and secondary control surfaces and ducts nearleading portion are supplied with warm, moisture reduced gas to avoidicing.

In a preferred embodiment gas is supplied under pressure to the ducts toprovide even outflow across the blown surfaces. Areas of increasedturbulence are provided with greater blowing gas flow by conventionalducting flow variation techniques.

Gas is withdrawn from suction ducts and gas under pressure is fed toblower ducts by using exhaust energy from propulsion engines.

A blower engine, preferably a turbine, is supplied with air from suctionducts. Demand valves at the inlet are opened automatically upon reducedpressure at the intake to supply ambient air to the auxiliary turbine.The air is turbine driven. Hot exhaust from the propulsion engine issupplied to the combustion section of the auxiliary turbine. Unburnedhydrocarbons in the propulsion engine exhaust are oxidized in the excessof air in the turbine. A small amount of fuel is sprayed into thecombustion chamber to further burn and drive the incoming air andexhaust gas from the main engine combustion chambers. These aresurrounded by gas spaces to keep the combustion temperatures relativelycool and to ensure complete mixing of the elements for completecombustion. Nitrogen oxides are avoided, and CO₂ and water vapor withexcess air result.

The gasses flow from the auxiliary turbine into a plenum whereoverpressures are released automatically to keep the turbine at maximumdesign operation. The gasses are cooled in a heat transfer refrigerationapparatus and are flowed through conduits to the blower ducts and outletslots where the gas is discharged under pressure rearward along theaerodynamic surface.

One object of the invention is the provision of a pollution reducingaircraft propulsion system having an aircraft with a fuselage andairfoil surfaces, an engine mounted on the aircraft, means connected tothe engine for propelling the aircraft and an input and output connectedto the engine for feeding and exhausting the engine, collecting meansconnected to the output for collecting matter therefrom, combustionmeans connected to the collecting means for receiving matter therefrom,intake means connected to the combustion means for flowing combustionsustaining material to the combustion means whereby combustion occurs inthe combustion means, exhaust means connected to the combustion meansfor conducting exhaust from the combustion means, ducting meansconnected to the exhaust means for conducting exhaust therefrom anddistribution means connected to the ducting means and connected to anexterior of the aircraft for distributing exhaust from the aircraft overaerodynamic surfaces of the aircraft.

Another object of the invention is the provision of blower ducting meanscomprising a plurality of parallel ducts mounted as structural membersinside skin surfaces of an aircraft and supporting the surfaces.

Another object of the invention is the provision of a boundary airblower engine with wing blower ducts connected to the intake compressorand blower means for withdrawing air before combustion and flowingwithdrawn air over aerodynamic surfaces of the aircraft.

Another object of the invention is the provision of a boundary airblower system with elongated ducts extending along a airfoil beneath itsouter surface and having passageways extending to the surface.

Another object of the invention is the provision of a boundary layerblowing system with suction ducts mounted in a forward upper portion ofthe airfoil and blower ducts mounted in a rearward upper portion of theairfoil.

Another object of the invention is the provision of a boundary layerblower system with blower ducts mounted along a lower surface of theairfoil.

Another object of the invention is the provision of wing blower ductshaving a tear-shaped cross section with a bulbous foward sectioncontaining a main passageway, and a tapered rearward section containinga restricted rearward directed passageway leading to a slot on a surfacefor blowing gas from the main passageway rearward over the surface.

Another object of the invention is the provision of a boundary layercontrol system having a blower duct in a trailing edge of an airfoilhaving a main passageway extending along the duct and having apassageway extending rearward then upward and downward to slots along aflap for directing blown gas rearward over the flap.

These and further objects and features of the invention are apparent inthe disclosure, which includes the foregoing and following specificationand claims and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a wing showing the blowing and suctionducts and intake and exhaust slots.

FIG. 2 is a cross sectional detail of a blower duct.

FIG. 3 is a cross sectional detail of a suction duct.

FIG. 4 is a schematic representation of an aircraft propulsion engineand an auxiliary turbine for drawing the blowing system.

FIG. 4A is a schematic representation of the wing.

FIG. 5 is a schematic detail of jet propulsion engine apparatus withpartial exhaust removal for feeding the auxiliary engine.

FIG. 6 is a detail of an auxiliary engine combustion chamber used with ajet engine exhaust source such as shown in FIG. 5.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1 a wing having a blown air system of the presentinvention is referred to by the numeral 1. The wing, is supplied withspars 2,4, and 6 which are of conventional design and which areschematically shown as I-beams. The wing as is conventional is providedwith primary aileron controls and secondary flap and slat controls toprovide increased lift in landing and taking off. The interior of thewing is provided with power lines actuators and fuel storage tanks in aconventional manner.

Conventional wing ribs, not shown, interconnect the spars. An airfoilsurface member 10 is made up of parallel plates on upper surface 12 andlower surface 14. The leading edge 16 of the airfoil is provided with aconventional slat structure. The trailing edge of the airfoil isprovided with a flap 18 to increase lift during relatively low speedoperation.

Blower and suction ducts are arranged as load-bearing stringers betweenconventional ribs, replacing the conventional stringers which supportthe airfoil skin 10. With reference to FIG. 1 and the detail in FIG. 2blower ducts 20 have tear-shaped cross sections 22. The passageway 24located in the bulbous portion of the duct supplies gas to restrictedrearward directed passageway 26 which releases a predetermined uniformflow of gas through slot 28. As shown in FIG. 2, forward and rearwardedges of the upper surface of the blower duct 20 are recessed to receivethe adjacent surface plate members in flush mounting.

Referring to FIGS. 1 and 3 the suction duct 30 has a "U" shaped crosssection. Passageway 32 pulls air directly from restricted slot 34. Uppersurfaces of the ducts 30 are recessed to receive adjacent edges of thesurface plates.

A rearward blower duct 36 supplies gas to upper and lower forks ofpassageway 38 which releases gas rearward through slot 39 over flap 18.

A conventional turbine type main propulsion engine is generallyindicated by the numeral 40 in FIG. 1. A compressor 42 forces air intoburner section 44. combustion products drive turbine blades in section46, which turn shaft 48, drawing the compressor blades in section 42 anddriving a propellor shaft 50 through the intermediate reduction gearing.

The engine exhaust flow into an exhaust plenum chamber 52 and outthrough an exhaust duct 54. An over pressure relieve valve 56 releasesexcessive exhaust gasses to the atmosphere.

An auxiliary engine 60 for blowing air purposes receives the exhaust gasfrom stack 54. Air from boundary layer suction ducts is drawn in throughconduits 62 into plenum 64. Automatic blow-in doors 66 admit ambient airwhen auxiliary engine intake pressure falls below ambient pressure. Acompressor in section 68 provides suction and drives the air towardblower to which further compresses the air into collection ring 72.Compressed air flows through air lines 74 and 78 past the fuel sprayerelements 76, which are served by fuel line 80.

A diffuser ring admits exhaust gasses from main exhaust duct 54 to thecombustion chamber 84, where unburned products from the main exhaust aremixed with fuel in an excess of air and are combusted, producing anexhaust with a high kinetic energy.

The exhaust drives fan blades 88 driving shaft 90, which in turn spinsthe compressor 68 and the blower 70. Blower 70 forces air out conduit 92which leads to some boundary layer blower ducts.

The exhaust of the auxiliary blower engine 60 passes into exhaust plenum94 and out through conduits 98 to the blower ducts. Overpressure reliefvalve 96 dumps excessive exhaust into the atmosphere in unusualoperating circumstances.

As shown in FIG. 5, the present system is used with a jet propulsionengine 100. Air is drawn through intake 102 and compressed in section104 by compressor blades in a conventional manner. Fuel is injected andignition occurs in combustion section 106. Turbine 108 drives compressor104. Exhaust and excess air are driven through exhaust pipe 110. A NASAscoop and duct 118 created in a high pressure area divert some of theexhaust through passageway 112 to collector ring 114, from where theexhaust flows through tube 116.

As shown in FIG. 6, the tapped main engine exhaust from tube 116 flowsthrough tube 120 to diffuser ring 122 and into a preheat area 124 of anauxiliary engine, shown in partial view. Fluids from tubes 126 and 128are flowed into annular combustion chamber 130. Air and unburnedmaterial from the main exhaust are recombusted with the added fuel andthe exhaust flows to plenum 132 for distribution through conduits to theblower ducts.

Although the invention has been described with reference to specificembodiments, it will be obvious to those skilled in the art that furtherembodiments may be constructed and used without departing from the scopeof the invention. The scope of the invention is defined in the followingclaims.

I claim:
 1. An aircraft pollution reducing propulsion airfoil systemcomprising a wing having upper and lower surfaces comprising wing skinplates extending longitudinally on the wing and being spaced one fromanother in chordwise directions, spars extending into the wing betweenthe surfaces, stringer ducts extending along internal sides of the wingsurfaces, the stringers having relatively rigid surface-supportingstructure and having outward directed openings extending across the wingsurfaces, interrupting the wing surfaces between edges of the wing skinplates, the ducts thereby forming stringer structural elementssupporting the wing skin plates, the outward directed openings of thestringer ducts being arranged perpendicularly to the wing surfaces in aleading portion of the wing and tangential to the wing surfaces in atrailing portion of the wing surfaces, suction means connected to thestringer ducts with perpendicular openings for drawing gas into theducts through those openings and blowing means connected to the ductswith tangential openings for flowing gas out of the tangential openings,combustion means connected to the suction means and to the blowing meansfor accelerating gas through the means.
 2. The system of claim 1 whereinleading portions of wing skin plates are inwardly curved toward thetangential openings.
 3. The system of claim 1 wherein each stringer ductwith a tangential opening has a tear-shaped cross section with a bulbousforward section containing a main passageway, and a tapered rearwardsection containing a restricted rearward directed passageway leading toa slot on a surface for blowing gas from the main passageway rearwardover the surface.
 4. The system of claim 1 further wherein the blowingmeans further comprises a blower duct in a trailing edge of an airfoil,having a main passageway extending along the duct and having apassageway extending rearward then upward and downward to slots along aflap for directing blown gas rearward over the flap.
 5. The system ofclaim 2 wherein edges of the wing skin plates are recessed in thestringer ducts.
 6. The system of claim 1 wherein the ducts comprisesuction ducts mounted in a forward upper portion of the airfoil andblower ducts mounted in a rearward upper portion of the airfoil.
 7. Thesystem of claim 6 further comprising blower ducts mounted along a lowersurface of the airfoil.